PROJECT SUMMARY (See instructions); The Flow Cytometry Shared Service (FCSS) at the University of Maryland Marlene and Stewart Greenebaum Cancer Center (UMGCC) offers flow cytometry equipment and technical expertise to UMGCC members conducting research in cancer biology and other areas of basic and applied science. Services are open to the entire University of Maryland campus, but UMGCC accounts for about 75 percent of the total use. FCSS provides full scale, state-of-the-art flow cytometry services, from functional and phenotypic analysis to cell sorting. Analytical instruments include a modern, fully digital, 3-laser Becton Dickinson (BD) LSR II flow cytometer, and two analog flow cytometers: a BD LSR 1 and a BD FACScan instrument. Cell sorting is conducted with (1) a BD FACSAria I digital instrument equipped with two lasers and seven-colordetection capability and (2) a BD FACSVantage SE instrument upgraded with BD's Digital Acquisition System (DIVA) and equipped with three lasers including a tunable krypton laser for 351 nm ultraviolet excitation. FCSS also offers users both operator-assisted and self-service data analysis on several platforms as well as experimental training and consultation to support project design for individual analytical or sorting experiments. The effectiveness of FCSS is evident from the steady increase of its utilization in recent years, the more than 50 principal investigators who are using the shared service, and the number of publications and National Cancer Institute-funded projects supported by experiments conducted with the help ofthe shared service. The goal of FCSS is to further increase the breadth and scope of its services by expanding cell-sorting capabilities;supporting novel, flow cytometry-based analytical applications;and strengthening cooperation with other UMGCC shared sen/ices to help introduce innovative, cutting-edge technologies to UMGCC investigators.